The Data Management and Biostatistics Core provides the Rush ADCC and each of its component cores with the ability to efficiently handle the large amounts of data they collect, maintains these data in efficient data sets with appropriate protection of confidentiality, and offers the skills needed to conduct well chosen statistical analyses of these data. The Core supports computer assisted data acquisition systems that are used for all data collection within the ADCC, except for small data sets. This computer-assisted approach offers improved data quality with fewer missing data and out-of-range values, opportunity to detect and correct the reduced number of errors that do occur in a timely fashion, more rapid availability of high quality data for analysis and elimination of the cost of double-entry data keying services. In the ADCC, these advantages of a computer-assisted approach have greatly outweighed its initially higher costs for programming and training. After collection, data from all ADCC cores are maintained in tables within a relational database management system. Reports generated from this system monitor the process of data transfer from the data collection staff to the database, track the progress of data collection, assess data quality, and monitor the process of correcting any errors. Multiple-level security procedures are used to assure the confidentiality and integrity of the data. The Data Management and Biostatistics Core provides investigators in other cores access to expert opinion on statistical issues and to appropriate analytic techniques. Because of the strong emphasis on collection of longitudinal data in the ADCC cores, there is corresponding emphasis on design and conduct of longitudinal statistical analyses. Use of expert statistical opinion from the Data Management and Biostatistics Core is emphasized not only in the conduct of analyses, but in study design as well. The Core does not directly conduct data analyses for the independently funded studies that utilize ADCC data, but provides guidance regarding the characteristics of the data and selection of appropriate analytic techniques. The Core also provides a mechanism for the ADCC to support and participate actively in data sharing and joint data management activities among all NIA-funded Alzheimer's Disease Centers.